The present invention relates to backpacks. More particularly, the present invention relates to an improved structure for a backpack which is more comfortable to the wearer and alleviates stress and strain to the wearer""s back, legs and shoulders.
In recent years, backpacking has become a very popular activity for serious hikers and for those simply interested in leisurely walks through the environment. Depending on a person""s physical condition and determination, the activity can be carried over gently rolling terrain, along wooded trails and even in mountainous areas. Many long hikes require large capacity pack shells that are capable of carrying food and supplies. Depending on the strength and size of the hiker, these pack shells can weigh in excess of 70 pounds. Backpacks including large capacity pack shells are in common use and are generally very tall and bulky. These backpacks typically include a waist band and a pair of shoulder straps for attaching the backpack to a person. When adjusted properly to a person, it is intended that the waistband carry 70% or more of the weight in the pack shell upon the wearer""s hips, with the remaining weight being distributed on the wearer""s shoulders.
It is important that the backpack be as comfortable as possible for the hiker to carry. Otherwise, hiking can become a miserable and exhausting experience. Unfortunately, not only does a hiker support the weight of the backpack, but when walking, the hiker receives substantial additional impact forces as the pack shell moves upwardly and downwardly with the wearer""s stride. As the hiker walks, the backpack undergoes a substantially sinusoidal motion as the pack shell rises upwardly and downwardly. Each time the hiker places weight upon one of his feet, the pack shell reaches it lowest point in the cycle at which time the pack shell imparts substantial impact forces, caused by the weight in the pack shell reversing its downward direction, to be transferred to the shoulder straps and weight belt of the backpack, and thereafter to the muscles and bones of the hiker. This is a particular problem when the hiker is walking downhill as the pack shell""s vertical movement, and downward velocity, is greater prior to being temporarily halted by a hiker""s foot striking the ground.
The physical shock upon the body of a hiker can be expressed by the mathematics and physics principals of force, impulse, momentum and kinetic energy. In accordance with Isaac Newton""s second law, the force upon the body of a hiker caused by the downward deceleration of the backpack is equal to:
force=(mass of backpack)xc3x97(change in velocity)
In other words, the downward deceleration and subsequent upward acceleration of the backpack exert a force on the hiker""s body with each step he takes. This force is in addition the downward force which is exerted substantially continuously on the hiker""s body by the weight of the backpack itself.
Meanwhile, the sum of forces over a very short time period is called an impulse force. For example, when a baseball is struck, the contact between bat and ball is called an impulse force. Similarly, when a backpack xe2x80x9cbouncesxe2x80x9d on a hiker""s back, equal and opposite impulse forces are exerted on the backpack and hiker""s body with each step that a hiker takes. Over time, the sum of these forces can cause substantial fatigue, tight muscles and possible damage to a hiker""s body after a considerable amount of time is spent hiking.
Furthermore, the mass and downward velocity of the backpack while hiking can also be expressed as kinetic energy by the equation:
kinetic energy=xc2xdxc3x97(mass of backpack)xc3x97(downward velocity of backpack)2 
In order to stop the downward movement of the backpack while walking, this kinetic energy must be absorbed through the body of the hiker.
In addition to the above described forces and xe2x80x9cshockxe2x80x9d imparted upon a hiker""s body, the upward and downward movement of the backpack imparts corresponding jarring of the pack shell and the contents within the pack shell. This substantial jarring can cause objects within the pack shell to move around and become unwantedly disturbed. This unwanted jarring can also damage fragile goods within the pack shell which is particularly troublesome where the objects carried within the pack shell are valuable or even invaluable, such as where the pack shell is constructed to carry a child.
There is thus a substantial need for an improved backpack which is light weight and comfortable to wear.
There is also a need for a backpack which reduces the amount of impulse forces which are imparted to the bones and muscles of a hiker when hiking.
Moreover, there is a need for a backpack which reduces the amount of jarring undergone by pack shell and the contents within the pack shell.
The present invention addresses the aforementioned problems by providing an improved backpack which incorporates an integral vibration damper.
The present invention provides for an improved backpack which is more comfortable for a hiker to wear by damping the downward velocity of the pack shell while walking. More particularly, the present invention is directed to a backpack which includes a vibration damper which connects the pack shell to the frame of a backpack. With each step, the downward movement of the pack shell is damped prior to the impact forces being transmitted to the wearer through the waist strap and shoulder straps of the backpack.
The present invention provides for a backpack including a frame, pack shell, shoulder straps and waist strap. The shoulder straps and waist strap attach the backpack to a person in typical fashion. The frame includes two or more vertical siderails and two or more horizontal rails. A backpack of the present invention further includes a vibration damper. The vibration damper connects the pack shell to the vertical siderails of the frame.
In a preferred embodiment, the vibration damper includes a cylindrical housing having a central chamber. Extending vertically through the vertical axis of the cylindrical housing is a central bore. The bore is configured for telescopic receipt of the siderail of the backpack frame. The vibration damper further includes a spring disposed vertically within the chamber of the vibration damper being annularly aligned with the bore and sidewalls of the housing. In a preferred embodiment, the chamber of the vibration damper is substantially air tight except for an air release valve which is located on either the housing""s sidewall or upper planar surface. Finally, the vibration damper is further constructed to connect to the pack shell of a backpack. To this end, the vibration damper includes a clip, loop, tab or strap for attaching to a pack shell to the backpack frame.
The backpack of the present invention preferably includes two or more vibration dampers which are attached to the backpack frame. When assembled, the vibration dampers are attached to the outermost siderails of the backpack frame by telescopically receiving the siderails through the vibration damper""s central bore. Formed annularly around the exterior of each siderail is a collar. Each siderail projects through the bores of a vibration damper so that the frame collars are disposed within the chamber of the vibration damper with the spring being placed in compression between the housing""s upper surface and the frame""s collar.
In a preferred embodiment, the vibration dampers are positioned toward the bottom of the frame sidewalls. This construction has the advantage of permitting most of the weight of the back pack and its contents to be carried by the lower portion of the backpack frame. In operation, the vibration dampers move vertically with the vibration dampers"" springs compressing as the dampers slide downwardly upon collars formed on the frame siderails. The pack shell is attached to the vibration dampers by a clip or strap or similar means such that the weight in the pack shell places a downward force on the vibration dampers and place the springs in compression. By placing the vibration dampers at the lower extremities of the frame, the weight of the pack shell is carried substantially at the lower portion of the frame.
In an additional embodiment, the vibration dampers are positioned upon the uppermost extremities of the frame""s outer siderails. The upper extremities of the siderails project through the bores constructed in the vibration damper""s lower surfaces to engage the vibration dampers"" springs. Again, a pack shell is attached to the vibration dampers so that the weight of the pack shell and any supplies or materials therein cause a downward force upon the vibration damper and the vibration damper""s central spring is placed in compression.
When a hiker wears the backpack of the present invention, the weight of the pack shell is transmitted to the frame of the backpack through the vibration damper. The upward or downward movement of the pack shell is transmitted through the spring thus damping the vertical movement of the pack shell relative to the frame and thus limiting the impulse forces transmitted by the pack shell upon the frame and one wearing the backpack.
In a preferred embodiment, the vibration dampers are substantially air tight except for an air release valve which projects through the housing sidewall or upper surface. As would be understood by those skilled in the art, the collar extends radially to engage the inner surface of the housing sidewall, inhibiting the ability of the vibration damper to move vertically upon the vertical siderails of the frame as any relative movement between the siderails and the vibration damper would change the internal pressure within the chamber. The air release valve provides the ability to adjustably allow air into and out of the chamber. This air release valve functions as an additional pneumatic damper similar to the pneumatic shocks on an automobile. Adjusting the ability of air to flow in and out of the chamber, allows one to adjustably control the damping of the vibration damper.
It is thus an object of the present invention to provide an improved backpack which is more comfortable to the backpack wearer.
It is an additional object of the present invention to provide a damper for damping the relative movement between the pack shell and the frame of a backpack while hiking.
It is still an additional object of the present invention to reduce the jarring which takes place within a backpack when hiking which would thus reduce the amount of movement or damage to objects within a pack shell when hiking.